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Review and Measurements of Totaldac d1-six DAC

AudioSceptic

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I may be misunderstanding here, but it’s the other way around. The way I read Amir’s subjective comments on this review was that, in spite of him knowing how poorly this DAC measures, he wasn’t able to hear much difference, and he has vast experience in ABX testing. So he is challenging his own bias, just from the other side of the fence, so to speak. Of the reviews I’ve read here on ASR, he’s usually very open and fair on this point.

I think in light of this fact, he’s fairly confident that our Totaldac-owning new friend won’t be able to identify the product in a blind test either, he’s basically said that even as badly as it’s implemented, it’s still effectively transparent, as are 99% of the products that get reviewed on this site. All that’s left to quibble over are price, build, features and aesthetics.
That's what I'm trying to clarify. I'm trying to understand saturdayboy's vociferous defence of the Totaldac but we will only know the truth if he does a controlled test (and so will he).
 
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amirm

amirm

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Maybe measurements first without evident ground loops.
You really didn't understand the answers I gave you, did you?

Here is a superbly measuring DAC with "evidence of ground loops:"

index.php


You want to explain to us why it is able to get such astonishing THD+N scores despite such "evidence" of ground loops as indicated by mains frequency of 60 Hz and odd harmonics thereof?

Then again, don't bother. If you are going to object to something, you need to understand your own technical arguments first.
 

sajunky

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You really didn't understand the answers I gave you, did you?

Here is a superbly measuring DAC with "evidence of ground loops:"

index.php


You want to explain to us why it is able to get such astonishing THD+N scores despite such "evidence" of ground loops as indicated by mains frequency of 60 Hz and odd harmonics thereof?

Then again, don't bother. If you are going to object to something, you need to understand your own technical arguments first.
No, Amir. You gave us suggestion that a leak in a DAC transformer could be a cause instead of ground loops. Not proven as you didn't investigate it any further. I do agree to the point that it could, but in addition to the ground loops. A critical moment for a proof that you had ground loops in the system was in the moment when you noticed both 50Hz and 60Hz components in FFT. For any electrical or electronic engineer with experience (not neccessary a degree) it is a proof and an indication that ground loops must be removed before starting any measurements. During the previous outburst of discussion in this matter you got helpers trying to prove otherwise, but they all vanished due to a lack of arguments.

Amir, I do appreciate you passion and determination to bring consistent measurements. Those who claim that it should be also listening tests are wrong. You don't have to do that, it is sufficient that you do it right. You are capable to learn on mistakes, it is good. You can do it right next time when you measure other European equipment. I am an optimistic, looking forward that opportunities are not wasted.
 

solderdude

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It is only proof that there are some 50 and 60Hz components in there. That could come from insufficient shielding, could come from leakage in the audio path or poor regulation, could come from induction by mains transformers or other magnetic fields, could come from ground loops.

I fully agree that one should investigate where it comes from it does not have to be a ground loop. It merely can be a groundloop amongst other things.
I suspect (expect) that Amir has sufficient experience with measurements and his test gear that he knows what to look for.
 

SIY

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It is only proof that there are some 50 and 60Hz components in there. That could come from insufficient shielding, could come from leakage in the audio path or poor regulation, could come from induction by mains transformers or other magnetic fields, could come from ground loops.

I fully agree that one should investigate where it comes from it does not have to be a ground loop. It merely can be a groundloop amongst other things.
I suspect (expect) that Amir has sufficient experience with measurements and his test gear that he knows what to look for.
You’re expecting this to have an effect after every substantive response has been ostentatiously ignored? You are far too nice of a person for this world.
 

Krunok

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It is only proof that there are some 50 and 60Hz components in there. That could come from insufficient shielding, could come from leakage in the audio path or poor regulation, could come from induction by mains transformers or other magnetic fields, could come from ground loops.

I see you guys have found yourself a new stubborn incompetent guy to loose some time this afternoon, ha? :D
 

KMN

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Not from the DAC which was operating at 50 Hz. But yes, APx555 has some 60 Hz leakage due to connection to the PC, etc.

Mains leakage is a fact of life in audio unfortunately. Many times though we have much bigger fish to fry which is the case with this DAC.

Also note that that my lab AC generator produces very clean power -- much better than what comes out of the wall in our house. So in that regard, this DAC is being given the benefit of the doubt versus your suggestion of using a transformer.

Hi. Does anybody know why 60 Hz mains leakage (or ground loop noise as the case may be) from the test equipment (or from interconnections with the test equipment in the case of ground loops) can show up in the measurements of some equipment and not show up in other equipment measurements? Presumably the test gear leakage, if that's what causes it, is essentially the same regardless of DUT.

An example would be the latest Matrix X-Sabre Pro MQA DAC. It has no evident traces of 60 HZ or harmonics. Compare that to the test of this Total DAC which would seem to indicate some amount of grid noise has somehow made it into the audio.

Is the 60Hz leakage (or whatever this is) in the test equipment somehow being absorbed or masked by the DACs not showing evidence of any leakage? ie are the better DACs apparently solving the susceptibility problems being introduced by equipment they are hooked up to?

By the way I am really loving it when you do the broadband fft scan from below 1Hz to up around 100kHz and how it can often reveal substantial spuriae in the ultrasonic region. Great work here, man!
 
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SIY

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Hi. Does anybody know why 60 Hz mains leakage from the test equipment can show up in the measurements of some equipment and not show up in other equipment measurements? Presumably the test gear leakage is essentially the same regardless of DUT.

An example would be the latest Matrix X-Sabre Pro MQA DAC. It has no evident traces of 60 HZ or harmonics. Compare that to the test of this Total DAC which would seem to indicate some amount of grid noise has somehow made it into the audio.

Is the 60Hz leakage in the test equipment somehow being absorbed or masked by the DACs not showing evidence of any leakage? ie are the better DACs apparently solving the susceptibility problems being introduced by equipment they are hooked up to?

By the way I am really loving it when you do the broadband fft scan from below 1Hz to up around 100kHz and how it can often reveal substantial spuriae in the ultrasonic region. Great work here, man!

Often it's inductive pickup from power transformers. Sometimes, it's inductive pickup from external fields as well. Sometimes, it's poor grounding practice in the DUT. That's why the loopback measurements are useful- they let you see what has the origin in the test equipment and what's coming from the DUT.
 

KMN

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Often it's inductive pickup from power transformers. Sometimes, it's inductive pickup from external fields as well. Sometimes, it's poor grounding practice in the DUT. That's why the loopback measurements are useful- they let you see what has the origin in the test equipment and what's coming from the DUT.

Indeed. And so why is some gear able to mask the effect so none of the grid frequencies show up while other gear is not? Is this some aspect of the DAC design or something else?

ie if this Total DAC measurement really does indicate leakage (please pardon my labeling this noise ingress as leakage while still presumably unproven origin) from the test gear must exist since that is the only place 60Hz could have originated since the DAC is run on 50Hz power, AND other DAC's are not showing the evidence of the 60Hz from the test gear, they would then appear to be suppressing a certain amount of noise injected from attached gear, no?

I think this noise suppression ability, if that is what we are seeing, seems like a highly desirable feature in audio equipment. Especially of the type likely to be connected to a PC or something noisy like that.
 
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solderdude

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Only the DAC itself runs on 50Hz, the power supply itself runs on 60Hz. Magenetic fields in close proximity to wires picks up 60Hz.
It could be not so great wire grounding in the TotalDAC or a relatively high resistance somewhere.
The only way to find out is when it is happening.
We are talking -115dB so submicroVolts, which is surprisingly easy to induce.
Maybe it is there, maybe it is not and a measurement error (likely)
In any case ... even IF it is there in reality one would have to cranck up the volume substantially to even begin to hear it.
 
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SIY

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It's not so much "masking" the effect as avoiding it in the first place. Layout and component choice are key.

I have on hand a piece of gear for review that has excellent measurements, except... a pretty big 60Hz spike at 60 dB down from the rated output. Opening it up, I immediately saw an obvious error in the grounding arrangement. If it were my unit (or I were the engineer responsible for the design), I'd go in and fix it. But as a reviewer, I merely report it and my analysis of the likely cause. If it were 110 dB down, I wouldn't bother, it's just not significant at that point.
 

KMN

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Fair enough solderdude. My concern is not necessarily that the flaws, shown here, would necessarily be audible under normal circumstances. But for example, Amirs lab may not be the worst case noise environment us readers may want to run our audio gear within... or some of us readers may not be as good at following equivalent best practice for setting up our complex audio rig cabling in ways that don't promote unwanted noises. There are so many variables to consider outside the lab.

I like the perception of increased flexibilty that comes with gear that is more difficult to induce noise problems within. I get to care less about understanding boring topics such as optimal hookup schemes , go crazy and hook things up in a way which is most convenient to me, generally have less worry about doing something wrong and suffering the consequences.
 

KMN

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It's not so much "masking" the effect as avoiding it in the first place. Layout and component choice are key.

This was my basic assumption but I figured I may as well run it by you experts. Thank you for responding.
 

solderdude

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My concern is not necessarily that the flaws, shown here, would necessarily be audible under normal circumstances. But for example, Amirs lab may not be the worst case noise environment us readers may want to run our audio gear within... or some of us readers may not be as good at following equivalent best practice for setting up our complex audio rig cabling in ways that don't promote unwanted noises. There are so many variables to consider outside the lab.

That is a very valid concern. Usually everything in a test environment is properly grounded as to avoid hum etc.
IRL situations with PC's and external DACs as well as amps or active speakers all connected to mains can turn into a nightmare with low level hums, weird 'noises' etc.
For all these variables one cannot test.
Weird common mode currents etc. are hard to find and diagnose sometimes. Certainly when one would want to solve something remote.
It can be as simple as 2 devices stacked which shouldn't be stacked, faulty interlinks but also weird ground loops.

You cannot test all situations under all circumstances.
For EMC tests there are also standard ways of testing and applying signals. One has to have standards. Reality may yet differ again from those test results.
I have had to tackle this kind of problems occasionally and know it can be a real pain to figure out where something comes from.
Everyone that ever worked with a scope has seen weird pulses one knows aren't there but its origin is difficult to pinpoint.

Measuring something properly, especially when more than 1 device is being used can be a challenge to say the least.
So can connecting various A-V components be.

Fortunately in most cases it works problem free or nasties are there but below audible levels.
 

sajunky

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Hi. Does anybody know why 60 Hz mains leakage (or ground loop noise as the case may be) from the test equipment (or from interconnections with the test equipment in the case of ground loops) can show up in the measurements of some equipment and not show up in other equipment measurements? Presumably the test gear leakage, if that's what causes it, is essentially the same regardless of DUT.

An example would be the latest Matrix X-Sabre Pro MQA DAC. It has no evident traces of 60 HZ or harmonics. Compare that to the test of this Total DAC which would seem to indicate some amount of grid noise has somehow made it into the audio
As others have already responded to this question, I'd like to add, that Amir equipment is first grade and, if any grounding problems were in the past it was properly dealt with. The only difference between other DUTs and Totaldac setup is an addition of a quality lab power converter, as Totaldac needs to be powered 230V. This device generates very clean power 50 or 60 Hz, perhaps far better than European wall socket, but it is the only things different to the standard system configuration that was already used in many test without of any signs of ground loops. It makes it a primary suspect. It could be as simple as an additional Y-capacitor that loops with other Y-capacitors, just giving an example of a very common cause. Ideally it should be only one Y-capacitor in the testing gear (including a DUT). As we don't know what is inside a DUT, it is better to not have any Y-capacitors in a testing gear power supplies.
 
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